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Computer System

Computer Programming (66111) An- Najah N. University Computer Engineering Department Luai Malhis , Ph.D , Introduction To Computer System. Computer System. Definition of a computer The computer is an electronic machine that performs the following four general operations: Input Storage

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Computer System

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  1. Computer Programming (66111)An-Najah N. UniversityComputer Engineering DepartmentLuaiMalhis, Ph.D,Introduction To Computer System Luai M. Malhis

  2. Computer System Definition of a computer • The computer is an electronic machine that performs the following four general operations: • Input • Storage • Processing • Output. Luai M. Malhis

  3. Computer Components • A computer consists of two main components : • Hardware the mechanical, magnetic, electronic, and electrical components making up a computer system • Software: which are written programs pertaining to the operation of a computer system and that are stored in read/write memory. • Following is an overview of the main hardware and software components in a computer Luai M. Malhis

  4. Computer Hardware • Input devices • System unit • Output devices • Storage devices • Processing Unit: The CPU and Main Memory Luai M. Malhis

  5. Input Devices • Enter data to be processed • Keyboard • Scanners • Mouse • Trackball • Touch screen • Microphone • Game Controller • Digital camera A B C D The rain in Spain Luai M. Malhis

  6. System Unit • Cabinet that houses all components • Motherboard • CPU • Memory modules System Unit CPU MemoryModule Motherboard Luai M. Malhis

  7. Output Devices • Enable us to see or hear the processed information • Monitor • Speakers • Printers Luai M. Malhis

  8. Storage Devices • Enable us to store data or information to be accessed again Hard Disk Drive FloppyDisk CD / DVD Drive Flash Drive Luai M. Malhis

  9. The CPU contains three parts: Arithmetic Logic Unit - ALU is where the "intelligence" of the computer is located. It performs all arithmetic operations such as addition, subtraction, multiplication and division. The ALU performs logical operations i.e. makes decisions by determining if a number is greater, less, or equal to the other number. An operation completes in nanoseconds, which is a billionth of a second. Registers: which are small storage devices holds instructions and operands needed by the ALU during operation execution. 3. Control Unit - This is the part of the unit, which directs information to the proper places in your computer, such as calculation of information by the ALU unit or to store and print material. The Central processing Unit • The CPU contains three parts: • Arithmetic Logic Unit - ALU is where the "intelligence" of the computer is located. It performs all arithmetic operations such as addition, subtraction, multiplication and division. The ALU performs logical operations i.e. makes decisions by determining if a number is greater, less, or equal to the other number. An operation completes in nanoseconds, which is a billionth of a second. • Registers: which are small storage devices holds instructions and operands needed by the ALU during operation execution. • 3. Control Unit - This is the part of the unit, which directs information to the proper places in your computer, such as calculation of information by the ALU unit or to store and print material. Luai M. Malhis

  10. The Memory Unit • The Main Memory: • Two types of memory contained on a chip are ROM (Read Only Memory) or RAM ( Random Access Memory). • ROM memory is installed on a computer by the manufacturer and can not be altered. ROM is the memory that determines all the basic functions of the operation of rge computer such as startup, shut down, and placing a character on the screen. • RAM is temporary memory, which stores programs during execution and also hold all information displayed on the monitor. RAM is read/write memory and it is much larger in size than ROM. Data disappears from the RAM when the computer is turned off or power is off. Luai M. Malhis

  11. Computer Software • Software - programs that enable the hardware to perform different tasks • Application software • Tools for getting things done Luai M. Malhis

  12. Computer Software • System software • Essential for platform operation and support Luai M. Malhis

  13. Computer Platforms: PCs and Macs PC • CPU – Intel, AMD • Operating system – Microsoft Windows Mac • CPU – Motorola • Operating system – Apple Mac OS Luai M. Malhis

  14. Application Software • Used to accomplish specific tasks other than just running the computer system. • May consist of a single program, such as an image viewer; • A small collection of programs (often called a software package) that work closely together to accomplish a task. • Independent programs and packages that have a common user interface or shared data format, such as Microsoft Office. Luai M. Malhis

  15. Programming languages • The machine language, which is the only languages understood by CPU. While easily understood by the CPU, the machine language is almost impossible for humans to use because they consist entirely of 0’s and 1’s. • A assembly language contains the same instructions as a machine language, but the instructions and variables have names instead of being just 0’s and 1’s. • High Level language Closely resemble human language Examples of high level languages are : Pascal, Fortran, Basic, Java, and C/C++. Programs written in high-level languages are translated into machine language by a compiler. Luai M. Malhis

  16. C/C++ Programming Lnaguage • History of C • Evolved from two other programming languages • BCPL and B • “Typeless” languages • Dennis Ritchie (Bell Laboratories) • Added data typing, other features • Hardware independent • Portable programs • 1989: ANSI standard • The C Lnaguage is Then developed to contain classes and other object Oriented features and named as C++. • Many Other Lnaguages currently developed that uses a synatx and symantics like C. • C/C++ is traditionally the first language a programmer learns. Luai M. Malhis

  17. How C++ Works Luai M. Malhis

  18. What is a program • A program is a set of instructions that a computer follows. • Example: computing the Area of Rectangle Get base Get Height Area = 0.5 * base * height • Steps to writing a program: Step 1. Think! (This is not optional.) Step 2. Organize your thoughts Step 3. Write them down in English Step 4. Translate them into C++ Luai M. Malhis

  19. Program Construction • Text Editor This is used to create the program in C++ form. Since this is the start or source of the other forms this is called a source file. (Source files end with .cpp. -- also used C and .cc.) • Compiler This translates the source file into a machine dependent file called an object file. The object file contains the instructions in a way that the machine can understand. The source file is in the C++ language (high level code) while the object file is in machine language (low level code.) • Link This is used to associate the object file with other necessary files to generate an EXE file Which contains the machine language. Luai M. Malhis

  20. Data vs. Information • Data vs. Information: • Data is a representation of a fact or idea • Number • Word • Picture • Sound • Information is data that has been organized or presented in a meaningful fashion. Luai M. Malhis

  21. Computers are Data Processing Devices • Four major functions: • Input data • Process data • Output information • Store data and information DATA IN INFORMATION OUT Luai M. Malhis

  22. OFF ON 0 1 0 0 1 1 1 0 0 0 0 1 0 0 0 0 1 0 Bits and Bytes: The Language of Computers • Bit • Binary digit • 0 or 1 • Byte • Eight bits • ASCII • Each byte represents a letter, number or special character Microchip Switch = 4 = A Luai M. Malhis

  23. How Much is a Byte? Luai M. Malhis

  24. Binary Language • Computers work in binary language • Consists of two numbers: 0 and 1 • Everything a computer does is broken down into a series of 0s and 1s • Switches: Devices inside the computer that can be flipped between these two states: 1 or 0, on or off Luai M. Malhis

  25. Switches • Non-mechanical devices in computers that open and close circuits • Types of electronic switches: • Vacuum tubes • Transistors: • Semiconductors • Integrated circuits Vacuum Tube Transistors Integrated Circuits Luai M. Malhis

  26. OFF 0 ON 1 Switches Representing Data • The on/off state of a switch represents one bit of data • Bit (binary digit) • On = 1 • Off = 0 OR = 1 bit 1 0 Luai M. Malhis

  27. The Binary Number System • Describes a number as powers of 2 • Also referred to as base 2 numbering system • Used to represent every piece of data stored in a computer: all of the numbers, letters, and instructions Luai M. Malhis

  28. The Binary Number System • Number systems are organized ways to represent numbers • Each number in one system has a corresponding number in another. 01011001 = 89 Binary Base 10 Luai M. Malhis

  29. Understanding Decimal Numbers • Decimal numbers are made of decimal digits: (0,1,2,3,4,5,6,7,8,9) • But how many items does a decimal number represent? • 8653 = 8x103 + 6x102 + 5x101 + 3x100 • What about fractions? • 97654.35 = 9x104 + 7x103 + 6x102 + 5x101 + 4x100 + 3x10-1 + 5x10-2 • In formal notation -> (97654.35)10 • Why do we use 10 digits, anyway?

  30. Understanding Binary Numbers • Binary numbers are made of binary digits (bits): • 0 and 1 • How many items does an binary number represent? • (1011)2 = 1x23 + 0x22 + 1x21 + 1x20 = (11)10 • (1010010) = 64+16+2 = (82)10 • (100010001) = 256+ 16+1 = (273)10

  31. Convert from Decimal tobinary For each digit position: • Divide decimal number by the base (e.g. 2) • The remainder is the lowest-order digit • Repeat first two steps until no divisor remains. Example for (13)10: Integer Quotient Remainder Coefficient 13/2 = 6 + ½ a0 = 1 6/2 = 3 + 0 a1 = 0 3/2 = 1 + ½ a2 = 1 1/2 = 0 + ½ a3 = 1 Answer (13)10 = (a3 a2 a1 a0)2 = (1101)2

  32. The Growth of Binary NumbersN is the number of bits in the binary number Mega Giga Tera

  33. Understanding Octal Numbers • Octal numbers are made of octal digits: (0,1,2,3,4,5,6,7) • How many items does an octal number represent? • (4536)8 = 4x83 + 5x82 + 3x81 + 6x80 = (1362)10 • What about fractions? • (465.27)8 = 4x82 + 6x81 + 5x80 + 2x8-1 + 7x8-2 • Octal numbers don’t use digits 8 or 9 Luai M. Malhis

  34. Convert an Integer from Decimal to Octal For each digit position: • Divide decimal number by the base (8) • The remainder is the lowest-order digit • Repeat first two steps until no divisor remains. Example for (175)10: Integer Quotient Remainder Coefficient 175/8 = 21 + 7/8 a0 = 7 21/8 = 2 + 5/8 a1 = 5 2/8 = 0 + 2/8 a2 = 2 Answer (175)10 = (a2 a1 a0)2 = (257)8

  35. Understanding Hexadecimal Numbers • Hexadecimal numbers are made of 16 digits: • (0,1,2,3,4,5,6,7,8,9,A, B, C, D, E, F) • How many items does an hex number represent? • (3A9F)16 = 3x163 + 10x162 + 9x161 + 15x160 = 1499910 • What about fractions? • (2D3.5)16 = 2x162 + 13x161 + 3x160 + 5x16-1 = 723.312510 • Note that each hexadecimal digit can be represented with four bits. • (1110) 2 = (E)16

  36. Converting Between Base 16 and Base 2 3A9F16 = 0011 1010 1001 11112 3 A 9 F • Conversion is easy! • Determine 4-bit value for each hex digit • Note that there are 24 = 16 different values of four bits • Easier to read and write in hexadecimal. • Representations are equivalent!

  37. 3A9F16 = 0011 1010 1001 11112 3 A 9 F Converting Between Base 16 and Base 8 352378 = 011 101 010 011 1112 3 5 2 3 7 • Convert from Base 8 to Base 2 • Regroup bits into groups of three starting from right • Ignore leading zeros • Each group of three bits forms an octal digit.

  38. Number System Conversion Table Luai M. Malhis

  39. Representing Letters and Symbols • There are codes that dictate how to represent characters in binary format. Most of today’s computers use the American Standard Code for Information Interchange (ASCII code) to represent each letter or character as an 8-bit (or 1-byte) binary code. • The ASCII code represents the 26 uppercase letters and 26 lowercase letters used in the English language, along with a number of punctuation symbols and other special characters, using 8 bits. Eight bits is the standard length upon which computers are built. • In the ASCII The representation for A is 41H (65) , B is 42H (66), a is 61H (97) and b is 62h (98). The Complete table is shown next slide Luai M. Malhis

  40. Computer ProgrammingAn-Najah N. UniversityComputer Engineering DepartmentLuaiMalhis, Ph.D,The C Language Basic Luai M. Malhis

  41. C Language Elements • Key Words - reserved words with special purpose that are part of the C/C++ language • Programmer Defined Symbols - words or names that have been defined by the programmer. May be variables, or constants. • Operators - Tell the computer to perform specific operations (ex: +,-, .. > &&). • Punctuation - begins or ends a statement (;) • Syntax - grammar rules for writing a C statement. Luai M. Malhis

  42. Some Definitions • Statement - instruction for the computer to perform, usually ends in a semicolon (;). • Variable - name given to a memory location that stores data that may change • Constant - data that does not change Luai M. Malhis

  43. Programming Errors • Syntax errors: violation of the syntax ( grammar rules ) of the programming language • The compiler gives an error message if the program contains a syntax error • Run-time errors: errors detected when the program is run • The system usually gives an error message during execution for run-time error • Logic errors: program compiles and runs normally, but does not perform properly. Caused by an error in the logic of the program Luai M. Malhis

  44. Special Characters Character Name Use // double slash to indicate a comment, everything to right is ignored. /* */ slash asterisk to enclose a comment # pound sign to indicate preprocessor directive < > brackets to enclose a file name for a preprocessor directive ( ) parentheses to enclose parameters for a function or change precedence { } braces to enclose a group of statements “ “ quotes to enclose a string of characters ; semicolon to end a statement Luai M. Malhis

  45. Comments • Important part of the program. • Non-executable (not compiled) statements • Describe the purpose of the program or parts of the program • Can be indicated by the double slash or the slash asterisk combination • // everything to the right of the double slash until the end of the line is ignored • /* encloses comment and requires a closing */ to end comment. • Provide documentation Luai M. Malhis

  46. Programming Process • Define the problem (most important step). • Purpose • Input • Processing • Output • Design an algorithm (often in pseudo code(English)) • Check logic • Write code, enter code, compile code • Correct any syntax errors • Run code with test data, correct any errors Luai M. Malhis

  47. Example • Suppose you want to calculate the area of a circle using the radius that a user enters. • Define Problem • purpose: the program is to calculate the area of a circle for a given radius • input: radius • process: area = 1/2 pi radius2 • output: area • Algorithm - • Display a message asking for radius // cout << “enter radius”; • Input the radius // cin >> radius; • Calculate the area= 0.5pr2 // area = 0.5 *3.14 raduis*raduis • Display the radius and the area // cout << “the area is “<< area; • Check Logic - does this algorithm fulfill the purpose. • Write code, enter the code, and compile it. Luai M. Malhis

  48. Variables and Constants • Data can be stored in RAM (Random Access Memory) to be used as needed. • Variables and symbolic constants are names for these memory locations. • Variables refer to memory locations in which the value stored may change throughout the execution of the program. • Constants refer to memory locations in which the values do not change. • Use a declaration to set aside memory space. Luai M. Malhis

  49. Identifiers (Variables) • Identifiers are names (or symbols) used by the programmer to refer to items such as variables, constants, functions. • Identifiers should be descriptive of what they stand for. Ex sum, total area • The “Name” used for identifiers must follow specific guidelines for C++ to be valid. Luai M. Malhis

  50. Identifier Naming Rules • The identifier cannot be a keyword, e.g. int, float, if, while, etc. • The identifier must be comprised of only letters (A-Z, a-z), numbers(0-9), the underscore (_) and the $ • The first character must not be a digit • C/C++ is case sensitive so total is not the same identifier as Total Luai M. Malhis

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